In recent years, information equipment including a touch panel display, as in a tablet PC, a smart phone, an electronic book reader, or the like has been the mainstream.
Any glass of a touch sensor glass, a cover glass, and a glass of OGS (one glass solution) is required to have a thin thickness and high strength, and a chemically strengthened glass which is subjected to a chemical strengthening treatment through ion exchange is used.
Strengthening characteristics of the chemically strengthened glass are generally expressed by a surface compressive stress (CS) and a depth of compressive stress (DOL: depth of layer).
A surface compressive stress layer formed by the chemical strengthening prevents a fracture occurring by an impact from being propagated. It is disclosed that phosphoric acid is contained in the composition thereof, and thus further damage resistance is obtained without degrading chemical strengthening characteristics (for example, see Patent Literature 1).